Regenerative Thermal Oxidizers: What they are, what they do, and more

Refurbished Regenerative Thermal Oxidizers (RTOs)

RTO systems destroy VOCs in industrial exhaust air to reduce air pollution.

A regenerative thermal oxidizer (RTO) is a type of air pollution control equipment that destroys hazardous air pollutants (HAP), volatile organic compounds (VOC) and odorous emissions created during industrial processes. A key difference between an RTO pollution abatement system and other oxidizer types is regenerative heat recovery, which makes the system extremely fuel efficient. For many reasons RTOs are the most common oxidizer technology in use today.

RTO Basics

RTO Operating Principles—RTO technology collects air emissions from industrial exhaust airstreams containing VOCs and HAPs, raises the airstream to high temperature to oxidize (convert) the pollutants into CO2 and H2O before releasing the clean airstream into the atmosphere. Like other oxidizer systems, time, temperature, and turbulence are the key to proper performance of an RTO.

Common Initial Questions

What does regenerative mean?

The term “regenerative” in regenerative thermal oxidizer is drawn from the type of ceramic media heat exchanger used in these systems. It is unique in that it captures heat from the exhausting, clean airstream during one cycle and releases the heat to the incoming, dirty airstream in the next cycle. The heat is captured (and released) from beds of ceramic media. The RTO incorporates switching valves to cycle the direction of the airflow through the RTO heat exchanger beds to enable regenerative heat recovery.

How efficient is a regenerative oxidizer?

Regenerative thermal oxidizers have a heat recovery (efficiency) of 95% typically. This technology has the lowest operating cost of all thermal oxidizer systems – not to mention the longest service life and highest reliability. It’s even possible for an RTO to operate with no auxiliary fuel use whatsoever if process VOC concentration levels are >3-4% lower flammability limit (LFL).

What industrial applications are best for regenerative thermal oxidizers?

Clean process airstreams with high air flow and low VOC content (<10% LFL) are ideal applications. Higher VOC concentrations can be tolerated, as well as organic/inorganic particulates with proper planning and design, and possibly filters. See our case studies for a sample of possible applications.

At what temperature does a regenerative thermal oxidizer operate?

RTOs typically operate at 1500o – 1600o Fahrenheit.

What is the dwell time in a regenerative thermal oxidizer?

RTOs typically have a 0.5 second to 1.0 second dwell time for most applications.

How Does a Regenerative Thermal Oxidizer Work?

Diagram illustrating how a regenerative thermal oxidizer works

The Simple RTO Process

An RTO uses seven basic steps for each cycle to heat the incoming dirty air, burn off pollutants and cool the exhausted clean air.

  1. Polluted air is drawn into the RTO fan
  2. Polluted air is pushed through a valve system into one (of two) beds of ceramic media
  3. Air is pushed through heated ceramic media; heating the air while cooling the ceramic media
  4. Heated air is pushed into a combustion chamber where pollutants are burned off
  5. Clean, hot air is pushed into second (of two) beds of ceramic media
  6. Air is pushed through the ceramic media; heating the ceramic media, cooling the air
  7. Clean, cooled air is pushed through open valve and exhausted into the atmosphere

LEARN MORE – How an RTO Works

regenerative thermal oxidizer system used for industrial air pollution control
RTO system oxidizing organic solvents and other pollutants.

Types of Regenerative Thermal Oxidizers

While RTOs can come in a few different configurations and layouts depending on the system’s requirements, the number of heat chambers used is the most common differentiator between types of RTOs. Also, there are variations in the types of valves used to reverse airflow direction. Some RTO technologies may not incorporate a traditional combustion chamber at all.

Essential differentiators between types of RTOs are:

  • Chamber Configurations
  • Heating Techniques
  • Air Flow Valves

LEARN MORE - Types of Regenerative Thermal Oxidizers

Applications of Regenerative Thermal Oxidizers

RTOs are used by manufacturers in a wide range of industries and applications. The Kono Kogs team has experience with practically every possible oxidizer application across many industries around the globe.

Industry Processes Using RTOs to Treat Emissions

  • Printing
  • Industrial Painting
  • Electronics Fabrication
  • Material Coating
  • Chemical Processing
  • Lamination
  • Can Production

LEARN MORE – RTO Industry Applications

How much does a regenerative thermal oxidizer (RTO) cost?

Typical RTO Cost: $25-$40/Standard Cubic Feet per Minute (SCFM) of air treated

This is a cost range for a new RTO system. Note it is based on RTO systems that are well designed and well built for the airflow volume being treated, in standard cubic feet per minute (SCFM).

For example, an 80,000 scfm RTO might be priced at 80,000 scfm/$25= $2,000,000

Some suppliers will be priced below this range but do your homework if they are significantly outside of this range. RTO systems are designed to treat a specific amount of a polluted air. The smaller units (<25,000 scfm) are nearer to the $40/SCFM value. Larger units achieve economies of scale and are nearer the $25/SCFM. When special features are required, like hot gas bypass, puff capture, special metals, etc. the cost will be higher.

The Total Cost of Ownership (TCO) is the initial capital investment in the equipment, plus installation costs, plus operating costs (fuel, electricity, and compressed air). RTOs have the lowest operating cost compared to other types of thermal oxidizers. Used, fully refurbished RTO systems from Kono Kogs can save you 40% or more in capital costs compared to buying new – with comparable guarantees and warranties.

Step one is choosing the optimal equipment for your application. The KKI team has over 150 years’ combined experience designing, reconditioning, and installing thermal oxidizer systems. We’re happy to perform a cost-benefit analysis for your project, explain your options including the trade-offs of each, and provide a professional recommendation.

A regenerative thermal oxidizer is a significant investment, but it doesn’t have to be a major long-term expense. Contact the KKI team for help selecting the most cost-effective system for your application.

Refurbished RTO installed at a manufacturing plant's exterior
Regenerative Thermal Oxidizers come in a range of sizes and configurations

Regenerative Thermal Oxidizer Design Factors

Certain RTO design factors can make a significant difference in both capital and operating costs:

  • Process air volume flowrate affects the size of the RTO unit, dampers and ductwork you’ll need.
  • Process air exhaust temperature determines the need for ductwork insulation, fan sizing, and affects expected operating costs.
  • Type & concentration of pollutants affects material of construction, heat exchanger efficiency, and greatly determines operating costs of electricity and fuel.
  • Complexity of RTO design affects how much RTO maintenance will be required. RTOs come in different designs, sizes and configurations.
  • Projected growth could make it smarter to install a higher-capacity system right away, rather than adding a second RTO in the future.
regenerative thermal oxidizers (RTO)
An inlet mixing box was added to this RTO system to handle two airstream temperatures.

RTOs Compared to Other Pollution Abatement Systems

Regenerative thermal oxidizers have many advantages over other oxidizer designs, but application in a specific process must be evaluated to determine whether it is a good match for your emission control needs.

Regenerative Thermal Oxidizer vs Thermal Oxidizer

In thermal oxidizers, air flows only one direction through the system. RTOs however create airflow reversals using dampers and control logic, which makes them much more thermally efficient.

Compared to other thermal oxidizer systems, regenerative thermal oxidizers are more efficient and reliable, and have a longer service life. However RTOs have a more complex build and are heavier, which can affect shipping, installation and commissioning costs.

RTOs are the best option for most industrial processes, however when 99.99% destruction of VOCs is a requirement, a thermal recuperative oxidizer may be the better solution.

LEARN MORE – Regenerative Thermal Oxidizers vs. Thermal Oxidizers

Regenerative Thermal Oxidizer vs Recuperative Thermal Oxidizer

The main difference between regenerative and recuperative thermal oxidizers is how each one recovers heat while operating. Recuperative thermal oxidizers use metal as the heat exchange material, while regenerative thermal oxidizers use ceramic media.

LEARN MORE – RTO vs. Recuperative Thermal Oxidizer

Regenerative Thermal Oxidizer Components

In many cases, KKI can help businesses comply with environmental regulations and reduce operating costs by repairing, rebuilding, or upgrading their existing regenerative thermal oxidizer. We have an extensive inventory of RTO parts including ceramic media, fans, burners, and much more, plus an in-house fabrication shop.

When the cost of regenerative thermal oxidizer repair outweighs the benefit, KKI can facilitate RTO replacement. We offer used “as-is” regenerative thermal oxidizers as well as fully refurbished systems with parts and performance warranties.

Available RTO components from Kono Kogs

  • Exhaust stacks
  • Combustion chambers
  • Media chambers
  • Media cold face support
  • Gas trains
  • Process ductwork/supports
  • Process T dampers
  • Hot bypass valves
  • Access platforms
  • PLC cabinets
  • Actuators
  • Insulation & cladding
  • Pneumatic controls

Kono Kogs RTO upgrades/services

The components and services above are by no means comprehensive. KKI can handle any RTO rebuild or replacement project you are facing. We invite you to send us your trickiest projects and look forward to the challenge!

regenerative thermal oxidizer manufacturers
Refurbished TANN RTO with a small footprint

Regenerative Thermal Oxidizer Manufacturers

The best-built RTOs make the best used RTOs. KKI selects only the best pre-owned regenerative thermal oxidizers and stands behind them with warranties that match new equipment Original Equipment Manufacturer (OEM) warranties. Check out our used RTO inventory from manufacturers including:

  • CECO ADWEST Technologies
  • Dürr MEGTEC Systems
  • CMM Group
  • REECO (Dürr)
  • TANN Corp.
  • Alstom

Common Questions When Researching RTO Systems for Pollution Abatement

RTO systems are advanced pollution control systems, so doing the required research before selecting the best one for your needs is essential. Below are some important questions our clients often consider before moving forward with purchasing a new or used system. Of course the engineering team at Kono Kogs is always available to answer questions and advise clients on the best RTO options for their needs.

For examples of our work, check out these refurbished RTO units case studies by Kono Kogs.

Is the RTO optimized for my exhaust airstream?
  • RTOs typically treat airstreams with a 0-10% Lower Explosive Limit (LEL)
  • RTO systems can handle 25% LFL airstreams, though hot gas bypass systems and other features may be needed
  • Is the ceramic media in the RTO optimized for my exhaust airstream to achieve?
    • Maximum thermal efficiency
    • Lowest pressure drop
    • Ability to handle organic/inorganic particulates
    Would a fuel gas injection system be a wise choice for this application?

    Fuel injection can provide significant fuel savings

    Does the RTO need to handle potentially corrosive emissions/halogens?
    • Special materials of construction may be required
    Do the local government codes require low NOX operation?
  • Low NOX burners can be retrofit for these applications
  • Case study: RTO solution for industrial NOx emissions
  • Are process emissions visible to the naked eye?
    • A puff capture feature can help eliminate visible emissions
    Does the RTO main fan use a variable frequency drive (VFD)?
    • VFDs are important for efficient operation, volume turn-down and idle operation
    Would an induced draft fan be a better choice than a forced draft fan?

    Solvents with a high boiling point can build up on a forced draft fan wheel

    Is the process sensitive to pressure pulses that can occur with poppet valve technology?
    • Rotary valve technology may be a better option
    Is the RTO skid mounted with little welding required in the field?
    • Ease of installation results in lower turnkey cost
    Are the PLC controls configured with remote access for troubleshooting?
    • Remote access can ease troubleshooting and reduce the frequency of service visits
    Is there a risk of ceramic media plugging due to condensing VOCs?
    • A bake-out feature can address organic compound build-up
    Is there a used RTO system available with the features needed?
    Featured Case Study

    Regenerative Thermal Oxidizer Treating Coil Coating Emissions

    Case Study: the used RTO from KKI had excellent performance numbers (99% VOC DRE) and provided significant capital cost savings compared to new equipment.

    Read the Case Study
    Regenerative Thermal Oxidizer Treating Coil Coating Emissions

    KKI is the leading global supplier of high-quality used air pollution control equipment. Our team has a 100% success rate meeting our performance guarantees and has earned repeat business from multiple customers. Whether you’re looking to get more efficient service out of your existing RTO or learn about your replacement options, KKI can help.

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